Worm or leech like things in my tank

Question
I have two goldfish, my tank is 20 tall, I use a biowheel filter system for 40 gallon(goldfish are messy) Ammonia is and has been a little high. I do a partial water (about 5 gallons) change every week or two. I was about to to do a water change this evening and I saw these dark brown worm like things in the rocks in my tank. YUK!! I Siphoned them out to get a better look. They are about two inches long when swimming like a water snake. The part that comes up in the water is long and thin while the back end has a flat suction cup thing on it that it seems to use to "walk". I do not know what they are I did put some plants in last summer and also added a rock last fall from my pond. They look like leeches to me but I really do not have any idea. I do know that they are the creepiest looking things that I have ever seen and I do not want them in my tank.

Answer
Hi Bonnie;

They do sound like leeches. They either came from the plants, the pond rock or one may even have been attached to your fish as a tiny balled-up one you couldn't see. Not all leeches attach to or feed on your fish but those that do can spread disease to your fish and cause anemia leading to illness and death so it is best to treat the whole tank for them. Look at your local fish store for a product that kills leeches. I know that a company called "Aquarium Products" makes one called "Clout" that is supposed to work. Hopefully you can find it or another that will do the trick. Use them carefully according to the label. Anything that will kill leeches can be pretty strong stuff.

At Your Service;
Chris Robbins